<s>
The	O
X	B-Device
Rendering	I-Device
Extension	I-Device
(	O
Render	O
or	O
XRender	B-Device
)	O
is	O
an	O
extension	O
to	O
the	O
X11	B-Device
core	I-Device
protocol	I-Device
to	O
implement	O
image	B-Algorithm
compositing	I-Algorithm
in	O
the	O
X	B-Operating_System
server	O
,	O
to	O
allow	O
an	O
efficient	O
display	O
of	O
transparent	O
images	O
.	O
</s>
<s>
It	O
was	O
written	O
by	O
Keith	O
Packard	O
in	O
2000	O
and	O
was	O
first	O
released	O
with	O
XFree86	B-Device
version	O
4.0.1	O
.	O
</s>
<s>
Its	O
design	O
was	O
influenced	O
by	O
rio	B-Language
,	O
the	O
windowing	O
system	O
for	O
Plan	B-Operating_System
9	I-Operating_System
.	O
</s>
<s>
The	O
core	O
X	B-Operating_System
Window	I-Operating_System
System	I-Operating_System
drawing	O
protocol	O
does	O
not	O
have	O
a	O
way	O
to	O
efficiently	O
draw	O
transparent	O
objects	O
:	O
A	O
computer	O
display	O
is	O
composed	O
of	O
individual	O
pixels	B-Algorithm
,	O
which	O
can	O
only	O
show	O
a	O
single	O
color	O
at	O
a	O
time	O
.	O
</s>
<s>
Thus	O
transparency	O
can	O
only	O
be	O
achieved	O
by	O
mixing	O
the	O
colors	O
of	O
the	O
transparent	O
object	O
to	O
be	O
drawn	O
with	O
the	O
background	O
color	O
(	O
alpha	B-Algorithm
compositing	I-Algorithm
)	O
.	O
</s>
<s>
However	O
,	O
the	O
standard	O
X	B-Device
protocol	I-Device
only	O
allows	O
drawing	O
with	O
solid	O
color	O
,	O
so	O
the	O
only	O
way	O
to	O
achieve	O
transparency	O
is	O
to	O
fetch	O
the	O
background	O
color	O
from	O
the	O
screen	O
,	O
mix	O
it	O
with	O
the	O
object	O
color	O
,	O
then	O
write	O
it	O
back	O
,	O
which	O
is	O
fairly	O
inefficient	O
.	O
</s>
<s>
Since	O
many	O
operations	O
require	O
transparency	O
(	O
for	O
example	O
spatial	B-Algorithm
anti-aliasing	I-Algorithm
,	O
especially	O
during	O
font	O
rasterization	O
,	O
and	O
transparency	O
effects	O
in	O
window	B-Application
managers	I-Application
,	O
such	O
as	O
transparent	O
windows	O
or	O
menus	O
)	O
,	O
this	O
limitation	O
caused	O
problems	O
,	O
and	O
Xrender	B-Device
was	O
implemented	O
to	O
address	O
it	O
.	O
</s>
<s>
It	O
provides	O
several	O
rendering	O
operations	O
and	O
also	O
does	O
alpha	B-Algorithm
blending	I-Algorithm
.	O
</s>
<s>
it	O
serves	O
primarily	O
to	O
implement	O
antialiased	B-Algorithm
fonts	O
,	O
but	O
for	O
example	O
KWin	B-Language
,	O
KDE	B-Language
’s	I-Language
window	B-Application
manager	I-Application
uses	O
it	O
to	O
draw	O
drop	O
shadows	O
and	O
translucency	O
in	O
case	O
OpenGL	B-Application
is	O
not	O
available	O
.	O
</s>
<s>
Text	O
is	O
drawn	O
by	O
loading	O
the	O
glyphs	B-Application
into	O
the	O
server	O
and	O
rendering	O
as	O
a	O
group	O
.	O
</s>
